1. Field of the Invention
This invention relates to a metals removing system and more particularly to a system for continuously removing metals from an aqueous stream.
2. Description of Prior Art
An example of a metal ion separation technique for the recovery of heavy metals is the use of liquid extraction system as a continuous technique to purify an aqueous stream. However, such liquid extraction techniques for removing metals from aqueous streams require large investments in mixer settler systems and are prone to large losses of liquid extractant due to carry over which poses downstream environmental problems. As a result relatively large quantities of liquid extract is lost and the and the process utilizes equipment with a large footprint.
It is desirable to provide a compact, economical metal removal system for the continuous removal of heavy metals either for environmental purposes or for mining operations which avoids the problems of large foot prints and loss of extractant over time.
The present invention provides a unique filtration device which continuously removes metals from aqueous streams through the use of a wicking fiber material containing a selected liquid extractant, which can capture the metal contaminants.
Wicking fibers have the ability to carry a liquid along their surface and to retain the liquid so it is not easily dislodged. Wicking fibers such as those disclosed in U.S. Pat. No. 5,057,368 are very small and well suited to the practice of the present invention. These generally hollow wicking fibers include internal longitudinal cavities each with a relatively small longitudinal opening extending to their outer surface. Through capillary action the individual wicking fibers rapidly draw the selected liquid, with which it comes into contact, through the internal cavities. The absorption liquid remains within the wicking fiber cavities and generally does not enter the space between the wicking fibers yet through the longitudinal openings the liquid is in communication with the fluid stream flowing past the wicking fibers.
Targeted metals are removed/recovered from the water stream by interposing a plurality of the wicking fibers which include in their internal cavities a liquid complexing agent having an affinity for the desired metals. The longitudinal extending opens in the wicking fibers permits the liquid retained in the wicking fiber cavities to interact with the aqueous stream and remove the targeted metals which are in the aqueous stream. A concentration factor induced molecular migration effectively conveys the undesirable metal molecules within the liquid extractant away from the aqueous stream to be cleaned, setting up a steady state concentration gradient with new metals continuously being absorbed and complexed within the supported liquid extractant.
This invention can be used in a customized fashion to either remove metals from a contaminated aqueous stream in a environmental remediation mode or to remove metals in a selective way in the mining/metals recovery area. Since this filter does not rely on liquid extraction in a traditional sense, wherein two immisicle liquids are mixed thoroughly together to provide as large of interfacial area as possible with the subsequent allowance for settling and separation of the two phases, the process with this supported phase can be accomplished in a much smaller volume and is more efficient and experiences far lower loses. The efficiency comes from the high interfacial area provided the liquid extractant. In the disclosed device the open space between the wicking fibers remain so that, in the aqueous stream, the flow can be through the media and the supported liquid extractant can come in contact most efficiently with the aqueous phase. A device according to the present invention provides for continuous use with or without periodic regeneration for the removing of metals from aqueous streams.